The importance of a neural pathway in the ventilatory response to exercise is very controversial. The results of experiments which have attempted to evaluate the role of a neural pathway by examining the ventilatory response to induced exercise before and after denervation of the proposed pathway have led to conflicting results. This project is designed to evaluate the role of a neural component using the denervation approach and will examine a number of factors which may be responsible for the observational controversy. If evidence for an important neural component is obtained, this project will attempt to further delineate the anatomical pathways traversed by this component. Very little is known concerning the role of suprapontile sites in the genesis of the exercise hyperpnea. The role of suprapontile sites will be evaluated by obtaining the ventilatory response to induced exercise before and after decerebration. Decerebration will be accomplished by cold block. This method should minimize any trauma. Also, since responses can be measured after rewarming each animal can act as its own control and any traumatic effects of the procedure evaluated. Thus this project will provide evidence on the role of a neural component, its pathway and the role of suprapontile sites in the modulation of the ventilatory response to exercise. The results of this project will add to our knowledge concerning the structure of the respiratory controller.